1. Field of the Invention
The present invention relates to a gas generator which may be used to inflate an automotive airbag or other safety restraint, and for providing gas under pressure to a device to be pressurized in other applications. More particularly, the present invention relates to such a gas generator that creates a pressure wave.
2. Description of the Related Art
U.S. Pat. No. 6,273,462 discloses an airbag inflator having a container for defining a chamber containing gas under pressure. The container includes a rupturable container wall or rupture disk which is rupturable to provide a gas exit through which gas flows outwardly from the chamber. The inflator includes means for producing a shock wave in the gas under pressure which ruptures the rupturable wall or disk. The shock wave producing means is spaced apart from the rupturable wall or disk and preferably is an igniter or detonator which is exposed to the chamber. The igniter creates a shock wave impulse that causes the rupturable wall or disk to rupture prior to the pressure in the container reaching the predetermined level at which the wall or disk is designed to rupture.
As specifically stated in the specification of U.S. Pat. No. 6,273,462, the rupturable disk was designed to rupture when the pressure in the inflator reached a predetermined level of 5,000 psi. The container was pressurized to an initial level of 1,054 psi, as can be seen at time 0 on the graph in FIG. 4. The activation of the igniter produced a shock wave in the gas in the container and increased the pressure in the container. The pressure in the container reached a maximum second level of 2,983.1 psi at 1 ms. The rupturable disk ruptured when the pressure in the container reached the second level which was much less than the predetermined level of 5,000 psi.
The inflator disclosed in U.S. Pat. No. 6,273,462 is subject to one or more of the following disadvantages:                1. The low fill pressure of the container does not optimize moles of gas relative to package size;        2. The rupturable wall or disk must be weakened to enable it to rupture at a pressure less than that at which it is designed to rupture; and        3. The igniter or detonator is exposed to the gas under pressure in the container and thus does not generate a high pressure wave for rapidly rupturing the rupturable disk at its design pressure before the gas in the container is heated to raise its average surrounding pressure to the design pressure of the rupturable wall or disk.        